Publication EP 1 213 130 provides a specific idea of this type of tyre, in which short reinforcing fibres, or inserts, are embedded in the tread in an oriented fashion so as to improve the mechanical properties of this part of the tyre in a given direction.
Publication U.S. Pat. No. 7,005,022 proposes a method for producing this type of component comprising oriented fibres, which entails first of all extruding a profiled element made of a rubbery material comprising isotropically oriented short fibres and then in a second phase, using a puncturing means that is more or less comb shaped, piercing the profiled element in a given direction in order, through the effect of the needles entraining the fibres, to orient some of the fibres in the direction of piercing.
This first type of method allows part of the result to be achieved, but does not allow all of the fibres to be oriented in the desired direction.
Publication EP 1 213 383 proposes another means for implanting the said inserts in a rubber component of a tyre tread structure.
This device comprises a hollow needle capable of penetrating the rubber component, and through which the reinforcing fibre runs, a moving support capable of performing a reciprocating movement and supporting the said needle, a cutting blade for parting off the fibre that is to be implanted, and at least two clamping means for maintaining and regulating the position of the fibre.
This device has the advantage of allowing all the fibres or reinforcing inserts to be implanted in a precise and controlled direction.
It is, however, noted that the clamping means provided in this device have the object of pushing and holding the fibre in order, upon each cycle, to force the fibre to run along inside the needle.
This mode of operation has the effect of placing the fibre under compression.
Despite the presence of guide means, this compression is likely to cause the fibre to buckle in those parts of its path where it runs freely, particularly when the fibre is a textile fibre with little resistance to this type of loading.
Other methods and devices aimed at embedding threads in composite materials used chiefly in the aeronautical industry are also described in publications of the prior art.
Publication U.S. Pat. No. 5,186,776 describes a similar device in which the thread, like in the device described earlier, is pushed using a nonreturn system positioned at the exit of the means that distributes the thread into the duct of a needle coupled to an ultrasonic excitation means.
Publication U.S. Pat. No. 5,642,679 describes a device the purpose of which is to insert a continuous thread through a multitude of layers of composite material in order to join them together. This device does not anticipate causing the thread to run inside the needle and does not provide cutting means capable, as will be seen later on, of creating a starter tail each time the needle is embedded in the material.